CN101505104B - A Symmetrical Rectification Circuit with Output Current Ripple Cancellation - Google Patents

Abstract

The invention discloses a symmetric rectifying circuit capable of counteracting output current ripples, which comprises a power transformer with four secondary side windings, two flying and balancing capacitors and two rectifier diodes. The symmetric rectifying circuit can effectively counteract the output current ripples by using the symmetric secondary side windings of the transformer and the flying and balancing capacitors without any additional active auxiliary element, so as to greatly reduce the capacitance value and volume of an output filter capacitor; and the symmetric rectifying circuit suppresses the voltage parasitic oscillation on a secondary side rectifying tube output junction capacitor, clamps the voltage stress of a rectifying tube at double output voltage, reduces the level of the withstand voltage of the rectifying tube and reduces the on-state loss of the rectifying tube. In addition, the effective reduction of the current in the secondary side windings of the transformer reduces the loss of the secondary side windings. Therefore, the symmetric rectifying circuit can effectively improve the overall conversion efficiency and the power density of the transformer while taking production cost into consideration.

Description

A Symmetrical Rectification Circuit with Output Current Ripple Cancellation

technical field

The invention belongs to the field of DC/DC conversion and rectification, and relates to a rectification circuit capable of realizing output current ripple cancellation and low rectifier tube voltage stress. More specifically, the present invention relates to a rectifier circuit comprising a power transformer with four secondary side windings and two flying balance auxiliary capacitors.

Background technique

The full-wave capacitive rectifier circuit (Figure 1) is widely used in high-current output occasions due to its simple structure, low rectifier voltage stress, no output inductance loss, and easy realization of rectifier soft switching working environment. . However, the high-frequency power transformer leakage inductance and lead inductance and the equivalent parasitic output junction capacitance of the secondary side rectifier can easily generate voltage parasitic oscillations during commutation, which increases the voltage stress of the rectifier, so it is still necessary to use it in practical applications. The auxiliary voltage buffer absorption circuit or the output rectifier tube with relatively high withstand voltage increase the auxiliary loss or conduction loss, reduce the overall conversion efficiency of the converter, and increase the production cost. The use of a full-bridge capacitive rectifier circuit (Figure 2) can effectively suppress parasitic oscillations and clamp the voltage stress of the rectifier on the secondary side to the output voltage, but the added rectifier will affect the conduction loss and increase the switching And driving loss and production cost. In addition, if the synchronous rectification technology is adopted to adapt to the occasion of high current output, the synchronous rectification driving of the upper transistor is difficult to realize. The secondary-side rectifier clamping circuit (Figure 3) effectively suppresses the voltage parasitic oscillation on the rectifier with the aid of the auxiliary balancing capacitor, and the voltage stress is clamped at twice the output voltage; the output current ripple is due to the bypass of the auxiliary balancing capacitor The effect is reduced to half of the current ripple in the rectifier tube, and the effective value of the current in the secondary side winding of the transformer drops, so a rectifier tube with a lower withstand voltage can be selected to reduce the conduction loss; a smaller output filter capacitor reduces the product volume; The conduction loss in the secondary side winding and the output filter capacitor can also be improved; in addition, the production cost can also be taken into consideration, no auxiliary active devices need to be added, and the production process can be simplified. However, in the case of high current, the output current ripple is still enough to affect the size and loss of the output filter capacitor.

Contents of the invention

The object of the present invention is to provide a symmetrical rectification circuit capable of offsetting output current ripples against the deficiencies of the prior art. The present invention utilizes the symmetrical structure and the effect of the flying-span balanced capacitor ripple bypass to effectively offset the output current ripple, and the capacitance and volume of the output filter capacitor are no longer affected by the output current ripple, thereby improving the overall efficiency of the converter. Conversion efficiency and power density, taking product cost into consideration.

The invention adopts the following technical solutions: a symmetrical rectification circuit with output current ripple canceling function, including a power transformer with four secondary side windings, two flying balance capacitors and two rectifying diodes. It is characterized by:

In the power transformer with four secondary side windings, the same-named end of the primary side winding is in the same direction as the same-named end of the first winding and the fourth winding of the secondary side, and is opposite to the same-named end of the second winding and the third winding. Towards. Define the terminal with the same name of the transformer winding as the positive terminal, and the other as the negative terminal, then the positive terminal of the first winding on the secondary side is connected to the negative terminal of the second winding, and connected to the anode of the output filter capacitor; the fourth winding on the secondary side The negative terminal of the secondary winding is connected to the positive terminal of the third winding and connected to the cathode of the output filter capacitor; the negative terminal of the first winding on the secondary side is connected to the cathode of the first diode, and the positive terminal of the fourth winding is connected to the first diode The positive end of the second winding on the secondary side is connected to the cathode of the second diode, and the negative end of the third winding is connected to the anode of the second diode.

For the two flying-span balancing capacitors, the positive pole of the first balancing capacitor is connected to the negative terminal of the first winding on the secondary side and the cathode of the first diode, and the negative pole of the first balancing capacitor is connected to the negative terminal of the third winding on the secondary side. The negative terminal is connected to the anode of the second diode; the positive terminal of the second balance capacitor is connected to the positive terminal of the second winding on the secondary side and the cathode of the second diode, and the negative terminal of the second balance capacitor is connected to the fourth winding on the secondary side. The positive end of the winding is connected to the anode of the first diode.

In the rectifier circuit of the present invention, the power transformer with four secondary side windings transmits energy to the output from the first winding and the fourth winding of the secondary side in the first half switching cycle, and the second winding and the third winding of the secondary side pass through the flying The current ripple on the output side is offset across the auxiliary balancing capacitor; in the second half of the switching cycle, energy is transferred from the second winding and the third winding on the secondary side to the output, and the first and fourth windings on the secondary side pass through the auxiliary balancing capacitor on the secondary side cancel the current ripple on the output side. The flying auxiliary balancing capacitor is used to bypass the AC, and at the same time clamp the reverse voltage stress of the first diode and the second diode.

The beneficial effect of the present invention is,

1. The present invention does not need to add any active auxiliary devices, and effectively offsets the output current ripple by using the symmetrical secondary side winding of the transformer and the auxiliary balancing capacitor of the flying span, so that the capacitance and volume of the output filter capacitor are greatly reduced; The voltage parasitic oscillation on the output junction capacitance of the rectifier tube on the secondary side is eliminated, the voltage stress of the rectifier tube is clamped at twice the output voltage, the withstand voltage level of the rectifier tube is reduced, and the on-state loss of the rectifier tube is reduced; in addition, the transformer secondary The RMS value of the current in the side winding is reduced, which reduces the loss of the secondary side winding. Therefore, the present invention can effectively improve the overall conversion efficiency and power density of the converter while taking into account the production cost.

2. The present invention can be applied to various topological structures of converters, such as soft-switching phase-shifting full-bridge circuits, full-bridge LLC resonant circuits and half-bridge LLC resonant circuits.

Description of drawings

Fig. 1 is a traditional full-wave capacitive rectification circuit;

Fig. 2 is a traditional full-bridge capacitive rectification circuit;

Figure 3 is a voltage clamping rectification circuit of the rectifier tube on the secondary side;

Fig. 4 is the symmetrical rectification circuit of the present invention with output current ripple canceling effect;

Figure 5 is the rectification circuit shown in Figure 4 applied to a soft-switching phase-shifted full-bridge converter;

Figure 6 is the rectification circuit shown in Figure 4 applied to a full-bridge LLC resonant converter;

Fig. 7 is the rectification circuit shown in Fig. 4 applied to the half-bridge LLC resonant converter;

Figure 8 shows that on the basis of Figure 4, the four windings on the secondary side of the transformer adopt an asymmetric structure.

Detailed ways

The purpose and effects of the present invention will become more apparent by describing the present invention in detail below with reference to the accompanying drawings.

Referring to Fig. 4, a symmetrical rectification circuit with an output current ripple cancellation function of the present invention includes a power transformer T with four secondary side windings, two flying balance capacitors C _a1 and C _a2 and two rectifier diodes D ₁ and D ₂ .

A power transformer T with four secondary windings, the end of the same name of the primary winding w _p and the end of the same name of the first winding w _s1 and the fourth winding w _s4 of the secondary side are in the same direction, and are in the same direction as the second winding w _s2 and the second winding The same-named end of the three-winding w _s3 is reversed. Define the terminal with the same name of the transformer winding as the positive terminal, and the other as the negative terminal, then the positive terminal of the first winding w _s1 on the secondary side is connected to the negative terminal of the second winding w _s2 , and connected to the anode of the output filter capacitor C _out ; The negative end of the fourth winding w _s4 on the secondary side is connected to the positive end of the third winding w _s3 and connected to the cathode of the output filter capacitor C _out ; the negative end of the first winding w _s1 on the secondary side is connected to the first rectifier diode D ₁ The cathode of the fourth winding w _s4 is connected to the anode of the first rectifier diode D ₁ ; the positive end of the second winding w _s2 on the secondary side is connected to the cathode of the second rectifier diode D ₂ , and the third winding w _s3 The negative end of is connected to the anode of the second rectifier diode _D2 .

The two flying balance capacitors C _a1 and C _a2 , wherein the anode of the first balance capacitor C _a1 is connected to the negative terminal of the first winding w _s1 on the secondary side and the cathode of the first rectifier diode D ₁ , the first balance The negative pole of the capacitor C _a1 is connected to the negative terminal of the third winding w _s3 on the secondary side and the anode of the second rectifier diode _D2 ; the positive pole of the second balancing capacitor C _a2 is connected to the positive terminal of the second winding w _s2 on the secondary side and the second The cathodes of the two rectifier diodes _D2 are connected, and the cathode of the second balancing capacitor C _a2 is connected with the positive terminal of the fourth winding _ws2 on the secondary side and the anode of the first rectifier diode _D1 .

The power transformer T transfers energy to the output from the first winding w _s1 and the fourth winding w _s4 on the secondary side in the first half of the switching cycle, and the second winding w _s2 and the third winding w _s3 on the secondary side pass through the auxiliary balancing capacitor C _a2 Offset the current ripple on the output side; in the second half of the switching cycle, the second winding w _s2 and the third winding w _s3 on the secondary side transfer energy to the output, and the first winding w _s1 and the fourth winding w _s4 on the secondary side pass through the flying The current ripple on the output side is canceled out across the auxiliary balancing capacitor C _a1 . The flying auxiliary balancing capacitors C _a1 and C _a2 are used to bypass the AC, and at the same time, the reverse voltage stress of the first rectifying diode D ₁ and the second rectifying diode D ₂ is driven by the flying auxiliary balancing capacitors C _a1 and C _a2 Clamped to twice the output voltage.

Referring to Fig. 5, the invention is applied to a soft-switching phase-shifted full-bridge converter. Among them, DC is the DC voltage source on the input side; Q ₁ to Q ₄ are the first to fourth MOSFET switch tubes on the primary side; _LR is the energy storage inductor on the primary side; C _B is the DC blocking capacitor on the primary side. In the first half of the switching cycle, the energy on the primary side is transmitted to the output through the first winding w _s1 and the fourth winding w _s4 on the secondary side of the transformer T. The first rectifier R _EC1 bears all the current ripple. Utilizing the AC bypass function of the secondary side flying auxiliary balance capacitor C _a2 , the current ripple in the first winding w _s1 of the secondary side and the current ripple in the second winding w _s2 are offset at the output side, and the second rectifier The reverse voltage stress of the tube R _EC2 is clamped by the flying auxiliary balancing capacitors C _a1 and C _a2 ; in the second half of the switching cycle, the energy of the primary side passes through the secondary winding w _s2 and the third winding w _s3 of the transformer T to output pass. The second rectifier R _EC2 bears all the current ripple. Utilizing the AC bypass function of the flying-span auxiliary balancing capacitor C _a1 on the secondary side, the current ripple in the second winding w _s2 of the secondary side and the current ripple in the first winding w _s1 are offset at the output side, and the first rectifier The reverse voltage stress of the tube R _EC1 is clamped by the flying auxiliary balancing capacitors C _a1 and C _a2 .

Referring to Fig. 6, the invention is applied to a full-bridge LLC resonant converter. Among them, DC is the DC voltage source on the input side; Q ₁ to Q ₄ are the _first to fourth MOSFET switch tubes on the primary side; _LR is the resonant inductance on the primary side; C _R is the resonant capacitor on the primary side; side magnetizing inductance. In the first half of the switching cycle, the first and third MOSFET switches _Q1 and _Q3 on the primary side are turned on, and the energy on the primary side is transmitted to the output through the first winding w _s1 and the fourth winding w _s4 on the secondary side of the transformer T. The first rectifier R _EC1 bears all the current ripple. Utilizing the AC bypass function of the secondary side flying auxiliary balance capacitor C _a2 , the current ripple in the first winding w _s1 of the secondary side and the current ripple in the second winding w _s2 are offset at the output side, and the second rectifier The reverse voltage stress of the tube R _EC2 is clamped by the flying auxiliary balancing capacitors C _a1 and C _a2 ; in the second half of the switching cycle, the second and fourth MOSFET switch tubes Q ₂ and Q ₄ on the primary side are turned on, and the energy on the primary side passes through The second winding w _s2 and the third winding w _s3 of the secondary side of the transformer T transmit to the output. The second rectifier R _EC2 bears all the current ripple. Utilizing the AC bypass function of the flying-span auxiliary balancing capacitor C _a1 on the secondary side, the current ripple in the second winding w _s2 of the secondary side and the current ripple in the first winding w _s1 are offset at the output side, and the first rectifier The reverse voltage stress of the tube R _EC1 is clamped by the flying auxiliary balancing capacitors C _a1 and C _a2 .

Referring to Fig. 7, the invention is applied to a half-bridge LLC resonant converter. The invention is applied to a half-bridge LLC resonant converter. Among them, DC is the DC voltage source on the input side; Q ₁ and Q ₂ are the first and second MOSFET switch tubes on the primary side; _LR is the resonant inductance on the primary side; C _R is the resonant capacitor on the primary side; L _M is the primary side of the power transformer T side magnetizing inductance. In the first half of the switching period, the first MOSFET switch _Q1 on the primary side is turned on, and the energy on the primary side is transmitted to the output through the first winding w _s1 and the fourth winding w _s4 on the secondary side of the transformer T. The first rectifier R _EC1 bears all the current ripple. Utilizing the AC bypass function of the secondary side flying auxiliary balance capacitor C _a2 , the current ripple in the first winding w _s1 of the secondary side and the current ripple in the second winding w _s2 are offset at the output side, and the second rectifier The reverse voltage stress of the tube R _EC2 is clamped by the flying auxiliary balancing capacitors C _a1 and C _a2 ; in the second half of the switching cycle, the second MOSFET switch tube Q ₂ on the primary side is turned on, and the energy on the primary side passes through the secondary side of the transformer T The second winding w _s2 and the third winding w _s3 pass to the output. The second rectifier R _EC2 bears all the current ripple. Utilizing the AC bypass function of the secondary flying auxiliary balancing capacitor C _a1 , the current ripple in the second winding w _s2 of the secondary side and the current ripple in the first winding w _s1 are offset at the output side, and the first rectifier The reverse voltage stress of the tube R _EC1 is clamped by the flying auxiliary balancing capacitors C _a1 and C _a2 .

Referring to Figure 8, on the basis of Figure 4, the four windings on the secondary side of the transformer T adopt an asymmetric structure, the number of turns of the first winding w _s1 and the third winding w _s3 are the same, which is N _s1 ; the second winding w _s2 and The number of turns of the fourth winding w _s4 is the same as N _s2 , and N _s1 is not equal to N _s2 .

It should be understood that: the above-mentioned examples are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many variations are possible. All deformations that can be directly derived or associated by those skilled in the art from the content disclosed in the present invention should be considered as the protection scope of the invention.

Claims (4)

1. A symmetrical rectification circuit with output current ripple cancellation, including a power transformer (T) with four secondary side windings, two flying balance capacitors (C _a1 and C _a2 ) and two rectifiers Diodes (D ₁ and D ₂ ); characterized by: Said power transformer (T) with four secondary side windings, the same-named end of the primary side winding (w _P ) and the same-named end of the first winding (w _s1 ) and the fourth winding (w _s4 ) of the secondary side In the same direction, it is opposite to the end with the same name of the second winding (w _s2 ) and the third winding (w _s3 ); if the identification end of the end with the same name of the transformer winding is defined as the positive end and the other is the negative end, then the first winding on the secondary side ( The positive end of w _s1 ) is connected to the negative end of the second winding (w _s2 ) and connected to the anode of the output filter capacitor (C _out ); the negative end of the fourth winding (w _s4 ) on the secondary side is connected to the third winding (w _s3 ) is connected to the positive terminal and connected to the cathode of the output filter capacitor (C _out ); the negative terminal of the first winding (w _s1 ) on the secondary side is connected to the cathode of the first rectifier diode (D ₁ ), and the fourth winding (w _s4 ) is connected to the anode of the first rectifier diode (D ₁ ); the positive end of the second winding (w _s2 ) on the secondary side is connected to the cathode of the second rectifier diode (D ₂ ), and the third winding (w _s3 ) is connected to the anode of the second rectifier diode (D ₂ ); The two flying-span balancing capacitors (C _a1 and C _a2 ), wherein the positive pole of the first flying-span balancing capacitor (C _a1 ) is connected to the negative terminal of the first secondary winding (w _s1 ) and the first rectifier diode ( The cathode of D ₁ ) is connected, the negative pole of the first flying-span balancing capacitor (C _a1 ) is connected with the negative terminal of the third winding (w _s3 ) on the secondary side and the anode of the second rectifier diode (D ₂ ); the second flying-span The positive pole of the balance capacitor (C _a2 ) is connected to the positive terminal of the secondary winding (w _s2 ) and the cathode of the second rectifier diode (D ₂ ), and the negative pole of the second flying balance capacitor (C _a2 ) is connected to the secondary The positive end of the fourth winding (w _s4 ) on the side is connected to the anode of the first rectifier diode (D ₁ ). 2. The symmetrical rectification circuit according to claim 1, characterized in that, the secondary side windings of the power transformer (T) have a symmetrical structure and have the same turn ratio. 3. The symmetrical rectification circuit according to claim 1, characterized in that, said rectifier diodes (D ₁ and D ₂ ) comprise common diodes, fast recovery diodes, Schottky diodes, and N-channel or P-channel MOSFET synchronous rectifier is any kind of semiconductor rectifier. 4. The symmetrical rectification circuit according to claim 1, characterized in that, the secondary side winding of the transformer can adopt an asymmetric structure, the number of turns of the first winding (w _s1 ) and the third winding (w _s3 ) are the same, is N _s1 ; the second winding (w _s2 ) and the fourth winding (w _s4 ) have the same number of turns, which is N _s2 , and N _s1 is not equal to N _s2 .

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